Mechanical seal Type29 APV Pump BB19C , introduction, description. This mechanical seal is equivalent or similar to the BIlli brand mechanical seal. Diameter 20mm type GLRD Serie BB19C 20mm,SS304(1.4301) Kohle/SS304/FKM,für APV Pumpe,Typ ZMA ZMB ZMH-1,ZMH-2,ZMH-4,ZM.